1. Field of the Invention
The present invention generally relates to an optical module having an optical waveguide structure, and in particular, to an optical module using an optoelectronic mixed Printed Circuit Board (PCB) or a flexible PCB in which an optical waveguide and an electrical printed circuit are integrated.
2. Description of the Related Art
Currently, there is an increasing demand for a technique for implementing high-speed data transmission over a short range for a compact device enabling transmission of video data using low power consumption. In addition, to solve electromagnetic wave inteference and wiring space problems occurring in electrical connections, a structure in which a transmitting module and a receiving module are optically connected is desired.
A Vertical Cavity Surface Emitting Laser (VCSEL) of a vertical light emitting type and a photodetector of a vertical light receiving type are typically used for achieving high-speed transmissions at low cost using low power. Such active optical elements of the vertical light emitting type or the vertical light receiving type are connected by a waveguide and a horizontal structure.
FIG. 1 illustrates a waveguide 100 applied to a conventional optical connection structure. Referring to FIG. 1, the waveguide 100 includes a board 110, a lower clad 121a, a core 122, and an upper clad 121b that are sequentially deposited on the board 110, and a light receiving element such as a photodetector 130 placed on the end portion of the upper clad 121b. A light source or optical elements of various forms in addition to the photodetector 130 may be placed on the end portion of the upper clad 121b. 
A groove for reflecting an optical signal traveling inside the core 122 to a light receiving surface of the photodetector 130 is formed under the waveguide 100 on which the photodetector 130 is placed. The groove includes a reflecting surface 123 inclined with respect to the core section that is perpendicular to the traveling direction of the optical signal. In other words, the reflecting surface 123 is inclined with respect to the section of the core 122 in order to reflect an incident optical signal from the core 122 to the photodetector 130.
A paper “Design and Development of Optoelectronic Mixed Signal System-on-Package” disclosed by Lyer et al. in IEEE Transactions on Advanced Packaging, vol. 27, no. 2, 278-285 in May 2004 describes another optical module including a two-branch waveguide, an optical fiber, and an Si mirror on a sub mount, and a photo diode on the Si mirror.
However, the conventional optical module requires a complex process, such as forming an inclined groove in a waveguide and forming a reflecting mirror in the formed groove, thus resulting in degradation in yield. Moreover, the optical module suggested by Lyer et al. integrates a two-branch coupler in a waveguide form and optical elements capable of receiving and emitting light on a sub mount, increasing its volume and causing a loss due to intervals between elements. As a result, there is increase in power consumption due to the loss.